package com.github.kennylee26.javaee.mvc.utils;

import com.google.gson.Gson;
import com.google.gson.JsonSyntaxException;
import com.google.gson.TypeAdapter;
import com.google.gson.TypeAdapterFactory;
import com.google.gson.reflect.TypeToken;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonToken;
import com.google.gson.stream.JsonWriter;

import java.io.IOException;
import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;

/**
 * <b>类名称：</b>DateTypeAdapter<br/>
 * <b>类描述：</b> GTM数字类型的日期字符串转Date类型 <br/>
 * <b>备注：</b><br/>
 *
 * @author kennylee <br />
 * @version 1.0.0 <br/>
 * @see com.google.gson.internal.bind.DateTypeAdapter
 */
public class DateTypeAdapter extends TypeAdapter<Date> {

    public static final TypeAdapterFactory FACTORY = new TypeAdapterFactory() {
        @SuppressWarnings("unchecked") // we use a runtime check to make sure the 'T's equal
        public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
            return typeToken.getRawType() == Date.class ? (TypeAdapter<T>) new DateTypeAdapter() : null;
        }
    };

    private final DateFormat enUsFormat = DateFormat.getDateTimeInstance(DateFormat.DEFAULT, DateFormat.DEFAULT, Locale.US);
    private final DateFormat localFormat = DateFormat.getDateTimeInstance(DateFormat.DEFAULT, DateFormat.DEFAULT);
    private final DateFormat iso8601Format = buildIso8601Format();

    private static DateFormat buildIso8601Format() {
        DateFormat iso8601Format = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.US);
        iso8601Format.setTimeZone(TimeZone.getTimeZone("UTC"));
        return iso8601Format;
    }

    @Override
    public void write(JsonWriter out, Date value) throws IOException {
        if (value == null) {
            out.nullValue();
            return;
        }
        String dateFormatAsString = enUsFormat.format(value);
        out.value(dateFormatAsString);
    }

    @Override
    public Date read(JsonReader in) throws IOException {
        if (in.peek() == JsonToken.NULL) {
            in.nextNull();
            return null;
        }
        return deserializeToDate(in.nextString());
    }

    private synchronized Date deserializeToDate(String json) {
        try {
            Long l = Long.valueOf(json);
            Date d = new Date();
            d.setTime(l);
            return d;
        } catch (NumberFormatException e) {
        }
        try {
            return localFormat.parse(json);
        } catch (ParseException ignored) {
        }
        try {
            return enUsFormat.parse(json);
        } catch (ParseException ignored) {
        }
        try {
            return iso8601Format.parse(json);
        } catch (ParseException e) {
            throw new JsonSyntaxException(json, e);
        }
    }
}
